为什么NetBeans在方法引用中说“不兼容的抛出类型IOException”？

Question

谷歌搜索没有任何结果，我想是因为这个错误对Java 8的新糖来说是新的。 当我捕获IOException时，NetBeans为什么告诉我“方法引用中不兼容的抛出类型IOException”？

错误的屏幕截图

完整方法代码

/**
 * Either extracts or returns the pre-extracted language file for the given locale
 * 
 * @param locale the locale 
 * @return
 * @throws IOException 
 */
private InputStream getLanguageFile(Locale locale) throws IOException
{
    File extracted = SaveConstants.inventSaveFileFor(Main.GAME_NAME, locale.toLanguageTag() + ".lang");
    if (!extracted.exists())
    {
        InputStream in = Resources.getLanguageStream(locale);
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        extracted.getParentFile().mkdirs();
        try
        {
            extracted.createNewFile();
            Writer writer = new FileWriter(extracted);
            reader
                .lines()
                .forEach(writer::write);
        }
        catch (IOException ex)
        {
            Logger.getLogger(Lang.class.getName()).log(Level.SEVERE, "Cannot extract language file for " + locale + ". Loading directly to map", ex);
            return in;
        }
    }
    else
        return new FileInputStream(extracted);
}

_{注意：我知道它会因为缺少返回而无法编译，但我希望在继续返回}

之前解决这个问题